Pusat Penelitian dan Pengembangan Pendidikan Matematika Realistik Indonesia Sekolah Tinggi Keguruan dan Ilmu Pendidikan


Teaching Subtraction Problem

Teaching a subtraction to children with a model of number line is quite difficult. Children have understood using it in addition problem. However, it is not guarantee that children can use it also in subtraction problem. It is depend on their strategy and how their thinking toward a certain question. So we have to choose a suitable question and construct their thinking across a good context – a real and imaginable situation by the children used in learning classroom.

There are two kinds of subtraction questions such as removal question and comparison question. Removal question seems rather easy to understand than comparison question, because it only works with different amount of number from one object. Meanwhile, in other case, comparison question involves two different objects but related each other. “John went into the store with $34 in his pocket and only had $16 remaining when he came out”, this is an example of removal problem (money problem). “Jasmine is 16 and her mom is 34. How much older than Jasmine is her mom?”, this is an example of comparison problem (age problem) . From both examples, we get the differences of removal question and comparison question if the criteria of part/whole context existed, the 16 is inside the 34, or not.

In addition, choosing a good context for subtraction problem is better if we choose a problem containing part/whole context. Because in teaching subtraction problem, we have to guide our children to think by themselves what the right idea is – counting on with adding on. Besides that, we also have to know our children formerly in order to know whether the context that we used is familiar for them or not. It is important to give the best learning process for children.

By Ekasatya Aldila Afriansyah


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